Carburetor



D. FIRTH CARBURETOR Feb. 13, 1940.

Filed Feb. I5, 1936 6 SheeyS-Sheet 2 Uff/a D. FIRTH CARBURETOR Feb. 13,1940.

Filed Feb. s, 193e 6 sheets-sheet s Feb. 13, 1940. D, FlRTH l 2,190,314

' CARBURETOR Filed Feb. 3, 1936 l 6 Sheets-Sheet 5 D. FrRTH 2,190,314

CRBURETOR 6 Sheets-Sheet 6 Feb. 13, 1940.

l Filed Feb. 5,1936

Patented Feb. `13, 1940 ,UNIT-ED STATES- PATENT OFFICE Theiinventionrelates generally to carburetors for internal combustion engines, andmore particularly to a downdraft carburetor.

v Carburetors generally may be divided into two 5 general classes so faras the position -of the throttle relatively to the fuel discharge nozzleand intake manifold `is concerned.,l i. e.,-a-posterior throttlecarburetor wherein thethrottle is positioned" behind the nozzle(between. the nozzle f and intake manifold), so that the nozzle is onthe low suction side of the throttle, Iand an anterior throttlecarburetor wherein the throttle is in? front of the nozzle (the nozzleis positioned intermediate the throttle and intake manifold),

` so that the nozzle or fuel .discharge device is `on the high suctionside' of the throttle. .Each 'of the two types of carburetors hascertainadvantages, and each has certain disadvantages. For

A example, therpostericr throttle carburetoris advantagleous inasmuch asthe meteringiof thefuel is accomplished on thelow suction side of. thethrottle, thereby makingit fairly. easyto calibrate the fueldischargemeans for partthrottle mixtures. A disadvantage of theposterior throttle carburetor, however,v is due tothe fact that thethrottle, being positionedy between vthe fuel discharge device and the.intake manifold, interferes with the flow of kfuel particularly forwide-open or full-power throttleposition, `thus causing poordistribution ofv the .fuel mixture to the cylinders. For this reason'the. anterior throttle carburetor isirnore advantageous so'far aswide-open or full-powerthrottle position is concerned, since thethrottledoesnot interfere with the flow of fuelv mixture.However,;beoause of the location of the fuel discharge devicev in thehigh suction zone of an anterior. throttle. ,carburetor, minute changesin ther orifices. orfjets of the fuel discharge devices causes.considerable change in thev mixture ratio. The present' inventionconstitutes an improvementlin the :form of carburetor disclosed in. mycopending application Serial No. 726,059, filed May 17,1934.

It is an object of thev present invention to prol vide a new andimproved carburetorembodying certain advantages of both the posteriorand the anterior throttle type carburetor, andA at the same timeeliminate disadvantageous features of yeach which were heretoforepointedl out.l

Another important object of the .present invention is toA provide acarburetorofthis rtype embodying new and improved means forincreasadjustment is interrelated to and governed by the" setting ofvthe choke valve.

`Another object is to provide a new and improved carburetor havingapluralityof accelerating pumps .conneoted -into the .main air and fuelpassage of thecarburetor in` such a manner as to insure properandeftioient mixture vof the fuel and air.

Another object .is to provide a carburetor wherein Aa throttle memberhaving a .main fuel.

discharge port at one of `its edges is arranged to cooperate with anemulsion tube in the `main, air and fuel passage to'deliver anefficiently vaporized fuel mixture.y

' Another object is to provide a carburetor having'an improved andsimplified. constructionproviding an accelerating pump having .a delayedfuel feeding action.

. Another object is toprovide a carburetor having. a new, improved andsimplied ,idling fuel supplymeansp Another `objectis to. provide acarburetor .having.. an,ew and `improved casingv construction wherebymanufacture, assembly,l inspection and repair are facilitated. v

. Other objects andv advantages will lbecome 'apparent fromthefollowingdescription, taken in connectionwith the accompanying drawings, inWhichl v Fig. 1Y is a vertical central section Vthrough apreferredA,einbodirnentI of. theinvention, showing the throttle inl apartially open position.

, Fig. 2 is` ,an inside view o f lone ofthe members which form, thefuelchamber. t

Fig.- Suis an enlarged vertical 4sectionalV view taken substantiallyalong theline 3--3 of Fig. 1.

Fig. 4 is an elevational rView of the float chamber with the. Side.member 0f the yfloat chamber .removed andwith. a portion 0f the.fuelsupply member showndin central `longitudinal section.

1 Fig. 4a is zalsectionall vview of the Afuel feeding member showingthechecl; valve formation.`

` Fig. 5 is a view similar to Fig. 4 taken substantially along the line5-5f0f Fig. 1V and showing onevf the ,aceleratinervmps l 5f? is a planview of a kretaining washer shown in Fig.. 5. y n Fig. 6 isafrontelevational View of the carburetor.

g Fig. '7 is a top plan view-of the carburetor.

Fig. 8 is ya side velevational View Iof -the carburetor asseen, from theright in Fig.,6.f

Fig. 9 is a ,verticalv sectional viewptaken substantially'alonggthe line9-9 ofY Fig. '7 and'v illustrating a preferred formuof idling fuelsupplyjet. .Fig. 101s an enlarged sectional View, takenlongitudinallyalong the axisfof: the throttley member and illustratingthe vacuum controlled means for everninathelfuel Supply.-

f ;.Fievv 1 1.15 a @View Showing-e1? elternriveferm of carburetor, aportion of the View being taken in vertical section through the rotativeaxis of the throttle member.

Fig. 12 is a view similar to Fig. 4 and illustrating in the fuel chamberan accelerating pump having an alternative form of actuating means. A

Fig. 13 is a sectional View similar to Fig. 3 and illustrating animproved means for adjusting the' idling speed.

Fig. 14 is a diagrammatic view showingthe relative position of the partsin section.

While the invention is susceptible of embodiment in many differentforms, there is shown ciples of the invention and is not intended to`limit the invention to the embodiment illustrated. The scope of theinvention will be pointed out in the appended claims.

In the form chosen for disclosure herein, the invention is embodied in adowndraft carburetor having a body It having a tubular portion I5forming a main passage I5, with a flange II on the portion I5 at thelower end of the passage I6 for connection with an intake manifold, andproviding a fuel chamber I8 at one side of the passage I5. Preferablythe fuel chamber I8 is formed in two sections I3 and I8, separable alonga vertical plane, with the section I8 vcast integrally with the tubularportion I5, and with the section I8" clamped in place against aninterposed gasket I3 by means of screws 2IL` Adjacent the upper end ofthe passage I5 a choke valve 2l is mounted on a rock shaft 22 foractuation by a conventional arm 23 on one projecting end-of the shaft.

In the passage I5 below the choke valve 2|, there is provided a throttlemember 25, mounted on atubular rock shaft 26 which is parallel to theshaft 22 of the choke valve. The location of these shafts is such thatthe axis of shaft 26 is perpendicular to the plane of separation of thefuel chamber sections I8 and I8, and one .end of this shaft projectsthrough bearing 21 into the upper portion ofthe fuel chamber I8 asshown` in Figure 1. At its .other end the shaft 26 projects through abearing 2B in the tubular portion I5 and carries at its outer extremitya conventional -actuatingarm 29.

Fuel is supplied to the fuel chamber I8 by a suitable conduit (notshown) which may be connected to a bushing 30 which is threaded througha boss 3l on the removable section I8 into the interior ofthe section asshown in Figure 2. vThe boss 3i) is preferably located so that thebushing axis is horizontal and parallel to the plane of separation ofthe sections I8 and I8, whereby the carburetor may be fitted for eitherright or left-hand mounting merely by provision of differently formedsections I8. Slidable in the bushing 30 is a valve 32 which, by means ofa float 33, is governed to maintain the fuel in the chamber I3 atsubstantially the level indicated by the line 34. Preferably the floatis mounted ona lever 33 which is pivoted on' 'a pin 33 carried by themember I8 so as to be positioned withinv and carried bythe removablemember IB" and to move in a plane parallel to the plane of separation ofthe sections I8 and I8".

In they preferred form of the invention, the fuel discharge meanscomprises a fuel duct or port 35 formed in the throttle 25, the port 35communicating at its inner end with an axially extending passage 36 inthe throttle shaft 25.v Y The passage in the throttle shaft extends intoY the portion of the shaft which vprojects into-the upper end of thefuel chamber I8 as shown in.l

Figure 1. Various means may be provided for supplying fuel from thelower portion of the fuel chamber to the port 35, although preferablysuch means assumes the form of a fuel feeding member 40 secured to thethrottle shaftv 25 so as to swing therewith, the member 40 havingapassage therethrough connecting at one end with; Y v

the passage 36 and at the other end with the surface of said memberbelow the fuel level in the chamber Itas hereinafter more fully de-`r`scribed, to form an inlet.

In the form illustrated in Figuresll to 10, avv tubular fuel feedingmember @Il is secured to thel projecting vend of the shaft 26 adjacenttothe bearing 2'I and extends radially from the shaftldown into the fuelchamber I8. AsleeVe-like piston 4I, slidable within the member iti), hasits lower end spanned by a wall 32 through which an axial bore 43 and anintersecting transverse bore 43' adjacent the lower endy provide a por-The fuel inlet pastion of a fuel inlet passage. n sage also includes kametering port M in a bushing I5 within theupper end of the member 40(Figure 4), an openingv 46 in the upper end ofv the member 4i), and aregistering port 4I (Figure 1) in the shaft 26 which opens into` thepassage 36. formed by the member 4I) to form an accelerating pump, thepiston being moved upwardly during opening movements'of the throttle'25by meansof an arcuate cam member IIB mounted The piston 4I cooperates'with the cylinder in the lower portion of the fuel chamber section I8'.The piston 4I atitslolwer end rides on the cam, member 48 so that duringswinging movement of the throttle 25 and its shaft 26 (in a clockwisedirection as vshownjin Figure 4) the piston is Ymoved upwardly or towardthe axis of the shaft 2E'. In the idle position of the throttle 25 asshown in Figure 4, the piston is projected or withdrawn to the lowerportion of the mem-'1 y ber 4U. An expansive coiled spring 49positionedV between a shoulder' 50 on the bushing l5 and an aperturedwasher 5I acts, through the washer 5I`and`an'interna1 shoulder 52against which.

it bears on the pistonk III, to move the piston 4I downwardly andmaintain the lower end thereof in contact with the cam 43. y

In order to prevent return Aiiow of fuel from..

a disk-type the accelerating pump cylinder, check valve 53 is positionedin the lower portion of thehollow piston II so as to 4be adapted toclose the port 43 during upward movement of the piston. This check valveis vof Ysufficiently light weight so astobe normally raised by incomingfuel and held in the position shown in Figure 4. Preferably a meteringpin 5d is carwill first be positionedinl the'port 44- so as to enlargethe area of the port and pass increased quantities of fuel and finallythe reduced portion.

55-"will;:be positioned in the portjM .soias.;toi.give the maximumelfectivenesst.y The "metering-pin vmay assumeA various forms dependingupon the characteristics desired'. j.

More-.eflicient proportioning of' the. fuel mixture in the higher speedranges is obtained in the present embodiment of the invention vthroughthe provision, in cooperation with vthe metering i action of the fuelsupply member 40, of a vacuum controlled fuel'metering means which isprefl erably mounted in the shaft 26 and governs the` eifective area ofthe passage 36,.. .This means in its preferred form is illustratedinFigures 1 and 10, andlcomprises a metering port 60 formed in the passage3bl adjacentA its junction with the port ofrthe throttle.v l

Themetering port 60.is controlled' by `a relatively small metering pin6I which extends axial-A ly through the port 66 from a piston 62 whichvisfslidably mountedfin a cylinder'portionL 62 within-.the shaft 26,andbeyond thefport 35 (see FigurelO)- i handend ofthe pin-6I lies withinand-'reduces the effective area of. port 'when the-piston 62 is in. itsright-hand position,` while movement ofy the piston to the left'projectsthe head 63 a substantial distance beyond `thelport 6I)l and increasesits eifec'tiverarea. The-.piston 62 moves between limits. fixed vron theleft byfa shoulder 84 and on theA right by a ,sleeve 65threaded into theshaft, and anexpansivecoil spring v66 ex-` tending through the sleeveandacting be#rv tween an end plug 61 in theshaft 26and1the piston 62.serves to.y urgethe meteringv pinBI.. to the left so as normally toprovide the maximum.

effective are'a for the metering port 6I). .If de'.

sired, a guidepin 68 may extend from v.theplug 6'! through Athe spring66. To `obtain vacuum.y controlled actuation of the piston 62,:apassager 69 formed inthe throttle 25 and the 'shaft 26, and extending inthesame directionasftheport 35, is connected throughan annular groove10.. and a port .1I to theright-hand .end ofv cylinder j 62. When thepiston 62 is in its .right-.handlpoi sition of Fig. 10, an annulargroove. 62? therein registerswith a vent passage 62e' tothe low suctionsidel of lche throttle 25 soasito .preventnow.` ofA fuel past the.piston. 4Thus the normal fuelx: mixture is proportioned eflicientlythroughout' the range of speedsby the cooperative actionof the meteringpins 54 and GIL'whichare controlled respectively bythe throttle positionand the vac uum conditions in the motor.

SinceA there -is always a passage of. fluid i through the port 35,l :theeffectofthe suction in lthe passage I6 will be lower on thefleft sidethan on the right side of the pistonl 62 .for theireason.

that the right side is a dead end.r A differential pressure is thus setup which accounts. for the resulting movement. of the `piston..62;y i

`For, purposes of 'sudden'acceleratiom the...V`

pumpingvaction of the fuel supply member 40 acts, of course, toforcefuel rapidly through the.

metering port 44,. which is openedhto vits greatest extentby theadvancingofritsmetering pin-S; 54,

and this additional fuel passes freely-' through of'fuel throughsupplying' further. fuel at such a point in the main passagel'i-.a'stoin'sure` thorough `and eiiicient mixture. offall. of the.. fuelyAnhenlarged headr63 in the left? in Figures 1, .5 rand* 9, and comprisesa pump 'I2 arranged: for actuation by the-shaft 26 of the throttle 25.In the form shown the pump I2 has a cylinder 'I3 formed integrallywithin the section. I8 radia1ly withrespect to the shaft 26 and having apiston 'I4y therein adapted for actionbyfa cam 'I5 `fixed to the shaft2l intermediatethe fuel supply member 4I) and the bearing/2l. rAt itslower'end, on the outside ofthe section I8', the oylinderis closed by athreaded plug 16', and above this plug fuel is admitted to a threadedportion 'I'I of the bore which forms the cylinder-,through an inlet port18. `Above the port 18j'inthe'portion 'I'I of the bore is threaded aplug I9 having an axial. passage Bil'l therethrough. opening into thespace immediately below the piston 113. In the passage 8D is locatedtaballr vcheck 8| `held against undue upward displacement from its seat 82by a spiderlike-washerf;83. A spring Silbetween the washer and thepiston I4 normally projects the piston 1,4', and alsotservesto hold thewasher 83 in. p0- sition.` y' s When the piston 'Mis depressed byactuation of. the throttle. 25', the fuel trapped in the cylinder byfthecheck valve 8 I. is forced upwardlythrough a ypassage 65. (Figs. 5 andl9) into a. chamber 85 (Fig. 9), through an orifice or jet 8'I andthence 0 outi of adisch'arge nozzle or jet 68 intothepassage` I6.Preferably such discharge is somewhat transversely of the passage justbelowthe level of: the throttle 25. n

After the contents of the .pump .'12 is dichargcd, further ow of fuelpast the checkvalve Si is preferably` prevented while f the` wide-openthrotu tle' position ismaintained. This end is attained by a springplunger 9i? slidably mounted axially inv the' piston 'I4 and. projectingdownwardly therefrom solthat in the discharge stroke ef the.

piston the endof the plunger. 95 passes through the spider-like'washer83 topress the ball check member 8|.y to its seated position. A springel, surrounding the plunger Within an enlarged bore 92e in the piston74, acts against a. flange 93 on the;plunger ,9G tourge the'plunger toits projected. position as limited by abutment of the ang'ezwith abearing Washer till whichsurrounds the plunger and isiixed in closingrelation tothe lower end of the bore 92. A reduced continuation. 95=1ofthe bore62fguidesthe upper end of thecplunger 90.

Ther fuelfor idling. purposesfis' in the present embodimentsuppliedy bymeans which includes the vfuel passages through the'acceleratingpump'l-2rto the discharge nozzle 68.I An adjustable primary air. supply tothe nozzle 88 isprovided for idling lpurposesby a horizontal bore 96.extending through the member I5 into the passage I8 above the level' ofthe throttle 25, with a Vertical bore 9.7 connecting the bore'll intothe passage between' thejet S'Iand the nozzle 88 (Fig. 9). An adjustingscrew .98 threaded into the bore 9d, andheld in Yadjusted position by aspring'li, cooperates Wththe-inner surfaces ofthe bores 96.and9tovarythe effective area of therpassages. By removal of a plug in thechamber 86, 'the jet, 81 may be changedto vary the size of. orifice,andthus by meansfofrthefjet. Si and theradjustment of screw 98, boththequantity of fuel 6and.qualityofifuel mixture may be adjusted.

. The. present. invention las embodied in-jthe 'form illustrated-fin-uFigures. 11 to lll' preferably provides meansv whereby anincreased Y idling.. speedis. ob-

`withtheair passing'throughpassa'ge I6' This cooperating fuel* supplyymeans. is best illustrated tained during use of the choke valve2|.-Thus,

as shown in Figures `1,621.7, and 8,.a vertically shiftable stop member|Il|I is mounted in. such a position that the idling position of .thethrottle 25 may be governed by. a plurality of stop shoulders |62, |63and |04 formed on the stop member. In the form shown the stop member |0|has a lower yoke |65 slidably embracing shaft 26 between the bearing 28and the arm 29, and a parallel upper yoke IE6 slidably embracing theshaft 22 between its bearing 'and a retaining washer IIll at the endthereof. Formed as a continuation of the throttle `arm 29 is an arm |08carrying an adjustable stopv screw |09 adapted for .selective engagementwith the vstop shoulders in accordance with the vertical setting of thestop member It.

When the choke 2| is closed, la radial arm ||Il fixed thereto engages alug I I. on the yoke |06, so as to raise the stop `member toward itsupper position of Figure 8, with the result that stop shoulder |56 iseffective and a fast idling speed is obtained. When the choke 2|' isopened the stop member IIlI drops to its lower position so that stopshoulder |62 is effective and the normalv idling speed results. In theuse of this device, the throttle 25 shouldbe opened as is doneyby mostdrivers in starting, thereby facilitating the elevation of the stopmember IUI. This cooperative action of the choke and the throttle is ofparticular advantage where an automatic choke is employed, although itsusefulness is not limited to such constructions.. The relative positionof the working partsk ma be seen in the diagrammatic view of the deviceshown in Fig. 14. The tubular portion is shown on the right forming themainpassage I6 and on the left is'the casing I3 which encloses the fuelchamber I8. Located in they passage |6 is4 the throttle 25 secured tothe throttle shaft 26.

with which it rotates. The shaft 25 extends into the fuel chamber I8wherein the fuel feeding member 40 is attached to it. When the shaft isrotated by means ofthe actuating arm 29, the throttle 25 is movedbetween. o and on positions and at the same time the fuel feeding memberMl is swung from one position to an-r other within the fuel vchamber I8.Integrally attached to the casing of the fuel chamber I8 isv the pumpl2, the outside of which is formed by the cylinder 13.

Fluid enters the fuel chamber past shown dotted at 32, and lls the.chamber to a level 34 where it is maintained by a float mechanism,omitted from the diagrammatic view of Fig. 14 for the sake' ofclearness, but which is shown in detail in Fig. 2. Fuel from the chamberpasses normally vthrough the axial bore 43 of the fuel feeding member6U, thence upward through the opening 46 into the passage 36 which liescentrally of the shaft26. ducted through the metering port and thenceoutward and downward through the port 35 of the throttle into thepassage I6.

When the throttle is closed, fuel for idling purposes is drawn from thefuel chamber I8 through the port "I8, past the check Valve 8| and thenceupward through passage 85, from which it is drawn downward and outwardfrom the discharge nozzle or jet 88 into the passage I6. A quantity ofair which is drawn through the bores 56 and S'I around the closedthrottle unites with the quantity of fuel drawn through the jet 8l intothe passage lI6 to form a combustible mixture for idlingpurposes.

the valve the discharge end lof the bore.

Fuel is then con-y when thethrotue 25 operiedga sumcient y' amount, anadditionalchargeof fuelissent into i the passage I6 byzineans ofthe pump12. To

produce this added charge,- the cam. 'I5 fixed to" the shaft 26drivesthepiston .14 downward by which action any quantity of fueltrapped below it within the cylinder I3 is forced upward and outwardthrough' the passage 85 and nozzle 88` N l' y into the air passage I6.

In the embodiment illustrated inFigure 11 of,`

the drawings, the. invention is embodied in a carburetor constructedgenerally along ythe lines of the embodiment of-'Figures 1 to 10, butwith the fuel feeding member 4i) serving as the sole. ,151 Inthisiform,the vpiston andy cylinderk 1 of the member 40 are made of agreater diammeans 'for providing a rapid feed for accelerating purposes.

eter so as to increase the capacity thereof,` and an and supporting lugsecured to the tube H5. By the use of the emulsion'tube I I5 suspendedrelatively close tothe` outlet port 35 of the throt-k tle, therelatively large quantity of fuel fed through thel port 35 is properlyAdirected and mixed with the air as it passes through the car-V L.; y, 3of,

bureting passage.

With the form of accelerating pump or fuel feeding member 40 employed ineither of the embodiments disclosed, la prolonged feeding action bythepumpmay be obtained through the provision of a resiliently mounted cam'48' asA shown in Figure l2. In this form, the cam 48 is pivoted on ascrewy |20 at the end which is enf gaged by the piston 4| in the closedposition" of the throttle. "At its otherend, the camis guided forpivotal movement by a slot |2| through which a screw |22 extends, andbeneath this end of the cam an expansive coiled spring |23 is positionedroll' about'a depending lug |24. Uponquick opening of the throttle' 25,the cam 48 is depressedsoas to compress the .spring |23, and by makingthe spring |23 slightly stronger than the `spring 49 of the pump, thecam 48i`s gradually elevated so as to cause a' prolonged dischargefromthe Dumpk i.

To provide an idling supply'of fuel, the embodiment of Figurevl'lpreferably utilizesthe main fuel supply passages jfromthemember45,'and to this end, as shown in Figure 13, an''idling fuel dischargeoriflce1|26 is .formed in the throttle 25lv from4 the bore of the" port35. downwardly through thesid'e of "the Vthrottle which facesvdownwardly in the closed throttle position.

Preferably the orice |26 is located adjacent to shown in Figi 13, anadjustable passage for air is preferably formed about the edge of thethrot- With the funn so tle adjacent tothe port 35, for the purpose ofregulating the richness `of the idling mixture'.`

Thus a threaded bore |21 is formed in the wall I3 so that the 'upperAand lower edges of the bore are located above and-below `they throttlefaces,

and bymeans of a screw |21 threaded throughy the` bore |21 an adjustableby-p-ass is formedv to vary the amount ,of air drawn ypast Saidkedge'ffy To effect an adjustmentlof theidling' mixture, the screw |21is screwed outwardly tof."

permit the throttle valve to shut tighter thereby to reducethe openspace at the edge cutting down 45 for fuel the passage of air rin orderto produce a richer mixture. The screw l|21 is screwed inwardly toprevent the throttle valve from shutting tightly thereby increasing theopening for air to produce a leaner idling mixture.

In the various forms illustrated'herein, the fuel feeding member 45 isprovided with an irregular opening 43|! through which the reduced andflattened end |3| of the throttle shaft extends. A cap nut |32 isthreaded onto the end ofthe shaft 26 so as to clamp the fuel feedingmember against a shoulder on the shaft formed by the reduced portion|3|. Thus rotary movement of the fuel feeding member with the shaftisinsured. Preferably, as illustrated in Figures 1 and 11, a groove |33 isformed inthe shaft intermediate the ends of the bearing 21, and a ventv|34 (Figure 5), or a vent |35 (Figure 11), is provided in the bodymember-so as to prevent any syphoning of fuel through 4the bearingshould leakage occur. Additional vent means is also provided for thefuel chamber |8, and such means may take the form of .a bored passage|36 (Figure 11) between the interiorl of `they casinglsection |8' andthe upper end of the passage I6, or it may be formed by an lup'standing'sleeve |31 extending through and riveted to the top of the removablesection |8".r

On the top of the sleeve |31 is secured a depend- .ing `skirt |38 whichshields the vent openings downwardly in the body passage asthe throttleis opened,'the fuel head on the orice may be varied, and if desiredtheorifice may be moved from a position above the normal fuel level in thefuel chamber to a'position below the normal fuel level.. By locatingthedischarge orifice in the throttle a simple construction is obtained, andas the throttle is opened'the fuel discharge orifice moves downwardlyvwith the incoming air so as to provide aprompt response to the demandBy'securing the fuel feeding member to the throttle shaft soxthat itswmgs therewith, there are no movablejoints inthe entire fuel supplypassage Wheredetrimental leakage could occur. Furthermore, the fuelsupply passage is effectively protected from the heat of the engine,

the portion in the lthrottle shaft and throttle the normal fuel feed. l

The vfuel' supply means provided is obviously such as to give eflicientand economical performance, and in, every embodiment is particularlyadapted for economical manufacture.

It is believed to be apparent that the form and construction o f thefuel supply chamber provided by the present inventionis `such as tosimplify Byy and reduce the costl of manufacture ofthe carburetor as awhole, and in addition, it facilitates the inspection of the variousoperating parts of the fuel supply means. The present formA of casingprovides' for the fixed mounting of the rone pump .12, as well as forthe positioning of the member llt within a rigid portion of the chamberlll so as to be housed and protected thereby while being readilyaccessible for inspection or repair. in addition, the float land the:supply connection are associated with the removable section so as tofacilitate such inspection .of the other parts, and in such mounting thefloat is fully housed and protected. l By reason of the relatively largearea capacity of the passage 3&3, andthe location of the metering porttu relatively close to the discharge oririce the opening of the port 60by operation vof its vaouuincontrolled metering pin results in aninstantaneous increase in the fuel feed, whereby to render the motormore responsive. l

orifice, means for supplying fuel from said chamber to said mainpassage, said means comprising a pair of accelerating pumps suppliedfrom said chamber and operatedto discharge fuel in repumps beingconnected to discharge through said orifice, and the-other of said pumpsbeing connected to discharge at another point in said `main passage.

2L A carburetor f comprising, in combination, a body providing a mainpassage and a l fuel chamber, a throttle in said passage having a fuelpassage rformed therein terminating in a' clischarge port adjacent toone edge of saidthrottle, a shaft supporting-said throttle and havingone end .projecting into said chamber, said end having an axial boretherein connecting with said fuel passage, a fuel feeding memberprojecting substantially radially from said end of said shaft andarranged'for swinging movement therewith, said member being arranged forfeeding of fuel to -said bore, a separate idling fuel supply means fedfrom said chamber, an accelerating pump 1 said chamber, arranged todischarge through said idling fuel supply means, and a cam on said endof said shaft for operating said pump.

3. A 'carburetor comprising, in combination, a body having a mainpassageand a fuel chamber at one side thereof, a throttle in said passagehaving a fuel passage therein terminating in a clischarge' orifice, arock shaft supporting said throttle and having an axial bore forming acontinuay tion of said fuel passage toward one end'of said shaft, saidend ofthe shaft projecting into said chamber, lan accelerating pumpmounted on said end of the'shaft to discharge into saidl bore and `toswing withr said shaft, means to operate said pump as it swings in theopening movement of said throttlej af second accelerating pump mountedin a iiXed position in said chamber, said second pump being arranged todischarge into' said main passage, and a cam on said shaft for operatingsaid .second pump.

' DAVID FIRTH.

